This invention relates generally to magnetic recording heads, and, more specifically, to magnetic recording heads used to store high density data in hard drives, tape drives and the like.
Magnetic media is widely used for data storage. Hard drives, tape drives, and floppy disks are all examples of magnetic data storage devices.
Typically, the magnetic medium comprises a thin film of magnetic material which can have various magnetic orientations in different domains on the surface of the film. Magnetic data storage requires the use of a read/write head capable of writing the magnetic field orientations of the magnetic domains. Such writing is typically performed by a magnetic circuit having a small gap, with a conductive wire magnetically coupled with the magnetic circuit. The gap is placed in close proximity to the magnetic medium surface.
Data encoded on magnetic storage surfaces is typically arranged in parallel tracks. The distance between adjacent tracks (track pitch) is one important factor which determines the data storage capacity of a magnetic surface. For maximum storage capacity, it is desired to make the track pitch as close as possible. The minimum track pitch, however, is limited by the physical dimensions of the magnetic read/write head used. Therefore, for maximum data storage capacity on a given magnetic surface, it is desired to minimize the width of the read/write head.
Another concern in the design of read/write heads is the fabrication geometry. Many head designs require the substrate on which the head is formed be cleaved and the cleaved edge polished. This allows the thin films adhered to the substrate surface to be oriented perpendicular to the magnetic data storage surface. This necessitates additional polishing steps so that the cleaved substrate edge is smooth. An example of such a read/write head is described in U.S. Pat. No. 5,075,956 to Das.
Another problem with magnetic read/write heads is that it is often difficult to manufacture the read/write pole of the head such that its dimensions are well defined and accurate.
U.S. Pat. No. 5,486,963 to Jones discloses a magnetic read/write head which uses a solenoidal type coil. The completion of the magnetic circuit in Jones""s head requires application of an additional vertical part of the pole piece to the polished edge of the cleaved substrate. This step renders Jones""s head more complex to manufacture and requires the step of polishing the cleaved edge. Another disadvantage of Jones""s head is that it requires that thin films be applied to the cleaved and polished edge.
U.S. Pat. No. 5,684,660 to Gray et al. discloses a magnetic read/write head which has a horizontal solenoidal structure and a vertical gap. Gray""s head is complex to manufacture due to a large number of plating and etching steps and the large number of elements comprising the magnetic circuit. Gray""s head also places the gap on top of the coil structure, which can be problematic because the coil structure is bumpy.
There exists a need for a sensitive magnetic read/write head which is simple to manufacture, which has a narrow geometry, and which has a read/write pole with well-defined dimensions.
Accordingly, it is a primary object of the present invention to provide a read/write head for magnetic data storage media that:
1) is simple to fabricate on planar substrates;
2) is narrow such that track pitch can be reduced;
3) does not require the substrate edge to be polished;
4) is sensitive to weak magnetic signals such that linear data density can be maximized;
5) enables a large number of heads to be planarized simultaneously;
6) requires a small amount of substrate surface area so that a large number can be manufactured on a single substrate.
These and other objects and advantages will be apparent upon reading the following description with reference to the drawings.
These objects and advantages are attained by a thin film magnetic head comprising a base layer of magnetic material disposed on top of a substrate with a first end of the base layer magnetically coupled to a first end of a core layer. The core layer is disposed on top of the base layer. An electrical conductor coil is wrapped around the core layer to form a solenoidal type coil. A return pole is disposed on top of a second end of the base layer and is magnetically coupled with the second end of the base layer. The return pole has a top return pole surface. A read/write pole is disposed adjacent to the return pole and is magnetically coupled with a second end of the core layer. The read/write pole has a top read/write pole surface which is coplanar with the top return pole surface. A layer of insulating material is disposed between the return pole and read/write pole. The insulating material defines a gap spacing between the return pole and read/write pole. The insulating layer is oriented at an inclined angle to the substrate. Preferably, the insulating layer is perpendicular to the substrate. The base layer, core layer, return pole and read/write pole comprise a magnetic material such as NiFe.
Preferably, the coil is electrically insulated from both the core layer and base layer. Also preferably, the surface area of the top return pole surface is greater than the surface area of the top read/write pole surface area.
The read/write pole and core layer preferably comprise a single, continuous layer of magnetic material. Also, the read/write pole and the core layer preferably have the same width. Preferably, the width of the read/write pole is narrower than the width of the return pole. The read/write pole can be surrounded on three sides by the return pole. In this case, the return pole is U-shaped.
Also, the head can be covered with a passivation layer which is preferably planarized to the plane defined by the top return pole surface and the top read/write pole surface.
In an alternative embodiment, the base layer is disposed in a groove in the substrate. The top surface of the base layer is flush with the top surface of the substrate. The groove can be a V-groove formed in a silicon substrate by an anisotropic etch.
An alternative embodiment of the present invention locates the coil around the core layer which is underneath a top layer which is made of magnetic material. The top layer is magnetically coupled to the read/write pole and the core layer is coupled to the return pole. The return pole and read/write pole are separated by an insulating layer which is oriented at an angle inclined with respect to the substrate. Preferably, the insulating layer is perpendicular to the substrate.
Preferably, the coil is electrically insulated from both the core layer and top layer. Also preferably, the surface area of the top return pole surface is greater then the surface area of the top read/write pole surface area. Preferably, the read/write pole and top layer comprise a single, continuous layer of magnetic material. The read/write pole and the top layer can have the same width. Preferably, the width of the read/write pole is narrower than the width of the return pole.
The read/write pole can be surrounded on three sides by the return pole. In this case, the return pole is U-shaped.
Also, the head can be covered with a passivation layer which is preferably planarized to the plane defined by the top return pole surface and the top read/write pole surface.
The present invention also includes a structure for a return pole and read/write pole. The return pole has a top return pole surface and a sidewall which has a predetermined height and is inclined with respect to a substrate. Preferably, the sidewall is perpendicular to the substrate. An insulating layer is disposed on the sidewall. The thickness of the insulating layer determines a gap spacing between the return pole and the read/write pole. The read/write pole comprises a magnetic material layer which is disposed on top of the insulating layer. The magnetic material layer is therefore parallel to the sidewall. A top return pole surface and a top read/write pole surface are coplanar and parallel with the substrate. The magnetic material layer has a thickness which is small compared to the height of the return pole sidewall. The plane defined by the top return pole surface cuts through the magnetic material layer. This assures that the thickness of the magnetic material layer determines the thickness of the read/write pole.
A method for making the return pole and read/write pole includes the step of producing a return pole which has a sidewall. The sidewall is preferably perpendicular to a substrate, but can also be inclined with respect to the substrate. The sidewall has a predetermined height. An insulating layer is deposited on the sidewall and a magnetic material layer is deposited on the insulating layer. The thickness of the magnetic material layer is less than the height of the sidewall. The return pole, insulating layer and magnetic material layer are then planarized to a plane parallel with the substrate which intersects the magnetic material layer and insulating layer. This assures that the read/write pole comprising the planarized magnetic material layer has a thickness which is determined by the magnetic material layer thickness. If the sidewall is perpendicular to the substrate, then the thickness of the magnetic material layer is equal to the thickness of the read/write pole.